This work attempts to explain the phenomenon of "group" from the standpoint of social psychology. The social-psychological research on the formation of opinions in the social field and some studies on individual behavior in social situations difficult claim to the reader aware of the problem of the relationship between "individual" with "others." It is a statement of the major theories about the group. An attempt to present the group - and individual - as a primary phenomenon of life in society. A clarification of the concepts of "group" and "group dynamics". A description of forms and structures of the groups. After referring to the group dynamics is studied in detail the main system of self: the feedback control system. A digression on the historical performance of the laboratories of the U.S. group dynamics and the Federal Republic of Germany is the exposure of the problems of these laboratories, and describes some of the techniques they applied.